The large numbers of people with mental illness in jails and prisons has fueled policy concern in all domains of the justice system. This includes police practice, where approximately ten percent of all contacts with the public involve a person with a mental illness. One approach to focusing law enforcement response in these situations has been the implementation of Crisis Intervention Teams (CIT). CIT is being implemented in jurisdictions across the country that are hoping to reduce injuries to officers and persons with mental illness, decrease arrests, increase diversion of persons with mental illness to the mental health system, and improve linkages to mental health services. Scant literature exists, however, examining the effectiveness of CIT and barriers to its implementation. The Chicago Police Department currently has pilot CIT programs in two of its 25 districts and is in the process of implementing CIT citywide over the next 18 months. In this application, we propose the initiation of a program of research that develops conceptual and methodological frameworks to support effectiveness research on CIT and other police based interventions for mental illness. To do so we will examine CIT as it is being implemented in Chicago, testing a preliminary model of its impact on officer and encounter level outcomes and district and community level factors such as CIT saturation (number of officers trained), availability of mental health resources, organizational support and leadership, and community characteristics that influence these outcomes. Because, the Chicago Police Department is just piloting this program, we have the unique opportunity to compare jurisdictions with limited CIT saturation with those that have fully implemented the program. We will apply both qualitative and quantitative methods and test different conceptualizations of model components. Qualitative interviews will be conducted with district level key informants and two time points. Quantitative data will be collected at baseline and one, three and six months. Cross sectional longitudinal analysis will examine District and individual level predictors of call outcomes (injuries, force, arrest, diversion, mental health service linkage) and how changes in saturation overtime are related changes in outcomes. This analysis will allow us to test different conceptualizations and measures of model components, test model interactions and paths, and determine effect sizes for a subsequent multi-site study. In the final phase of the project we will begin dialogue with four urban jurisdictions to discuss our findings and the applicability of our model and methods to their experiences with CIT, and subsequently develop collaborations for the multisite study. Although only limited evidence of effectiveness is available, CIT is being adopted by jurisdictions across the county in an effort to improve law enforcement's response to persons with mental illness. This study will allow us to test CIT effectiveness and develop much needed methodological and theoretical frameworks to support subsequent research on police based interventions for mental illness. This program of research will inform policy and practice aimed at improving officer, consumer and public safety and increasing access and linkages to mental heath treatment for persons with mental illness. [unreadable] [unreadable] [unreadable]